This invention relates generally to circuit breakers, and more particularly to circuit breakers for use with rotary contact assemblies.
Circuit breakers are used to interrupt a flow of current when current exceeds a specified value. Such a condition is sometimes referred to as a short circuit condition or an overcurrent value. In a short circuit condition, the circuit breaker robustly separates a pair of contacts that, under normal operating conditions, conduct the current. Separating the contacts electrically isolates the circuit wiring and associated circuit components from potentially damaging currents. At least some known circuit breakers are thermally or magnetically actuated.
In at least some circuit breakers, when the contacts are separated, an electrical arc may be undesirably generated between the contacts. In addition, within at least some circuit breakers, during a short circuit interruption, a dielectric breakdown may occur between the components. Continued operation of the circuit breaker with components that have dielectrically deteriorated, may be detrimental to the performance of the circuit breaker, may contribute to a poor transfer of the arc within an arc chamber, and over time, may limit the ability of the circuit breaker to isolate the components in a robust and timely manner.
To facilitate extending a useful life of the circuit breaker, at least some known circuit breakers use rotary contact assemblies, including iso bearings. The iso bearings facilitate shielding mounting springs on the face of the rotor and facilitate a smooth rotation of the rotor during circuit breaker mechanism operations. However, because of a relative position of the iso bearings with respect to the circuit breaker, the iso bearings do not facilitate protecting conductive rotor parts positioned along a perimeter of the rotor.
In one aspect an iso bearing for a circuit breaker is provided that comprises an inner surface, an outer surface, and a body extending therebetween, the inner surface comprising a pair of bosses and a pair of openings, the outer surface comprising at least one boss, and the body comprising a pair of rotor protective flaps.
In one aspect a rotary contact assembly is provided that comprises a rotor assembly comprising a plurality of pins, a linkage assembly, and a pair of rotor halves, each rotor half comprising an inner and an outer surface and a perimeter, the outer surface comprising a plurality of bosses. A contact arm configured to be mechanically and electrically coupled to the rotor assembly inner surface by the plurality of pins and the linkage assembly. A plurality of iso bearings mechanically coupled to the rotor assembly outer surface by the plurality of rotor bosses, the iso bearing comprising a pair of rotor protective flaps partially circumscribing rotary contact assembly perimeter to facilitate shielding the plurality of pins and the link assembly.
In one aspect a circuit breaker is provided that comprises a pair of electrically insulative cassette half pieces comprising a cavity therein, a plurality of electrically conductive straps positioned within the half piece, and a rotary contact assembly positioned in the cavity. The rotor contact assembly is positioned in the cavity and comprises a plurality of pins, a linkage assembly, and a pair of rotor halves, each rotor half comprises an inner and an outer surface and a perimeter, the outer surface comprising a plurality of bosses. A contact arm is configured to be mechanically and electrically coupled to the rotor assembly inner surface by the plurality of pins and the linkage assembly. A plurality of iso bearings mechanically coupled to the rotor contact assembly outer surface by the plurality of rotor bosses, each iso bearing comprises a pair of rotor protective flaps partially circumscribing the rotary contact assembly perimeter to facilitate shielding the plurality of pins and the link assembly. An operating mechanism is configured to separate the conductive straps and the contact arm, and a plurality of arc chambers are coupled to the half pieces.